1. Technical Field
The present invention relates to a device which identifies whether a consumable product connected to electrical equipment is an authorized product or a substandard product.
2. Description of Related Art
It is necessary for electrical equipment to attach a consumable product, which satisfies a predetermined standard. The reason is that electrical equipment may not operate properly, or may be damaged, or may not be used safely, if a substandard consumable product is attached thereto. To achieve attachment of a consumable product within the standard to electrical equipment, a system, which identifies whether a consumable product attached to electrical equipment is an authorized product or a substandard product, has been developed: (see Patent Document 1)                Patent Document 1: Japanese Laid-Open Patent Publication TOKUKAI No. HEI 5-198293        
A consumable product disclosed in this document is connected to electrical equipment through a communication terminal. When a consumable product is attached to the electrical equipment, the electrical equipment transmits a request signal through the communication terminal. When receiving the request signal, the consumable product provides process data calculated from this signal through the communication terminal. The electrical equipment checks the process data provided from the consumable product, and identifies whether the consumable product is an authorized product or a substandard product.
In the system, which identifies whether a consumable product is an authorized product or a substandard product as mentioned above, a substandard product may provide the same process data as the authorized product. The reason is that the request signal provided from the electrical equipment into the consumable product and the process data provided from the consumable product into the electrical equipment can be determined by detecting signals passing through the communication terminal. For this reason, a manufacturer can manufacture substandard consumable products, which provide process data similarly to an authorized consumable product. This causes a problem that users wrongly use such substandard consumable products as authorized consumable products.
In this system, complicating relation between the request signal and process data can more surely detect substandard products. However, even if the request signal and process data are complicated, the system has certain relation between the request signal and process data. Accordingly, if this relation is determined, the process data to be calculated from the request signal can be obtained. For this reason, even if relation between the request signal and process data is highly complicated, substandard products cannot be detected in ideal condition. In addition, if relation between the request signal and process data is complicated, a circuit for calculating this relation is also complicated. This causes increase of component cost. As a result, there is a disadvantage that the cost of a component for identifying whether an authorized product or a substandard product becomes high. Such a component for identifying whether an authorized product or a substandard product does not serve as essential operation of an electrical equipment unit and a consumable product. Accordingly, it is important to surely detect substandard products with as low cost as possible.